1. Field of the Invention
The present invention relates to a photometry device for measuring the luminance of an object and, more particularly, to a photometry device of a camera, which is used in automatic exposure control of the camera.
2. Description of the Related Background Art
As a conventional device of this type, a device described in Japanese Patent Application Laid-Open No. 3-15726 is known. As shown in FIG. 10A, the device comprises a photometry/colorimetry circuit 51, a light-receiving element selection switch 52, and a CPU 53. Photometry is done by selecting a light-receiving element of the photometry/colorimetry circuit 51 by the light-receiving element selection switch 52 in accordance with the color of the object to be photographed or the light source color, and the CPU 53 calculates the proper exposure value. As the light-receiving elements of the photometry/colorimetry circuit 51, a luminance photometry element N, red photometry element R, green photometry element G, and blue photometry element B are mounted on a single chip, as shown in FIG. 10B.
Currently, a built-in photometry device of a camera or the like is so-called a reflected-light exposure meter. The photometry device measures light reflected by the object illuminated by a light source, and calculates the proper exposure value. The photometry device of this type can easily attain photometry from the photographer side, but is readily influenced by the light reflectance (to be simply referred to as reflectance hereinafter) of the object as compared to an incident-light exposure meter which directly measures a light beam which becomes incident on the object at a certain position of the object. That is, the reflected-light exposure meter recognizes an object with higher reflectance to be lighter than an object having lower reflectance even under the same illumination, and gives a relatively underexposure value to the object with higher reflectance and a relatively overexposure value to the object with lower reflectance. As a result, both a whitish object with high reflectance and blackish object with low reflectance are expressed by neutral gray in a picture.
Recently, a photometry device which divides the object field into plural regions and measures the object field by divisional photometry, analyzes the scene to be photographed by comparing the luminance values of the plurality of regions, and gives an exposure value which is relatively independent from the reflectance of the object has been developed.
Meanwhile, some scenes cannot be discriminated by divisional photometry alone: for example, a sunset glow scene, and a daytime scene with the same composition. These two scenes are determined to be nearly the same scene by normal divisional photometry. However, the exposure value should be adjusted to the sunset glow sky in the sunset glow scene even when it is too underexposure a value for the foreground object, while the exposure value should be adjusted to the foreground object in the daytime scene.
Hence, the conventional photometry device switches light-receiving elements in accordance with the object color or light source color, and performs photometry using light-receiving elements having different spectral sensitivities in the sunset glow and daytime scenes, thereby giving proper exposure values to these scenes.
However, with such a conventional photometry device, the photographer himself or herself must discriminate the object color or light source color to switch the light-receiving elements, resulting in complicated operations.